Calgary police say they understand that high school students want to celebrate the end of classes, but warn that going too far can lead to legal problems that could haunt them in the future.

A water balloon fight involving 500 students on Tuesday left a park near William Aberhart high school in a mess, while pranks at other Calgary high schools included pulling a fire alarm, setting small fires and igniting smoke bombs.

"If it is something that they're doing that's construed as criminal in nature it's certainly something where you know there could be follow up or, indeed, criminal charges," Sgt. Rob Brown said Wednesday. "Or something could come along afterwards, and I mean the last thing that we want on a happy day when you're finishing school is that you're getting your last day of your school career and the police are involved."

Brown said officers expected pranks, and  extra patrols were deployed around high schools this week for the end of the school year.

In  an email sent to parents, William Aberhart principal Tamie Annis Johnson raised concerns about the significant mess left behind after the water balloon fight in Canmore Park, adding the school received numerous complaints from people in the area.

The email also said that there were instances of dangerous driving that led to at least one student suffering minor injuries after being hit by a car.

Ali Tod, a Grade 12 student from William Aberhart, was back at the scene on Wednesday to help clean up.

"It's definitely not good for the community and I feel like I owe it to the school to clean up and help maintain their relationships that they have with the community, and the school's proud of that."

According to the email the school also had to deal with smoke bombs,live crabs and lobsters placed in toilets and on stairwells, as well as other acts of vandalism.